Field of the Invention
This invention relates to electrocardiographic electrodes for deriving weak voltage from a living body and, more particularly, to a multi-electrode type electrocardiographic electrode structure, which can be easily held in close contact with the living body and also can be inexpensively manufactured.
Prior Art
As is well known in the art, electricity is induced in the living body by the activities of the heart, brain and muscles.
Particularly, electricity generated in the heart is used for the diagnosis of the heart by recording a weak voltage induced on the skin of the living body using an external electrocardiograph. When the electrocardiograph is used, its input section has to be electrically coupled to the living body by having electrocardiographic electrodes in close contact with the skin of the living body.
FIGS. 6 and 7 illustrate a prior art electrocardiographic electrode which is to be held in close contact with the skin of a living body. Reference numeral 1 designates this electrocardiographic electrode.
The electrocardiographic electrode 1 comprises a substantially disk-like base member 2. The base member 2, as shown in FIG. 7, has an adhesive surface 2a so that the electrocardiographic electrode 1 can be held in close contact with the skin M of a living body, as shown in FIG. 8. The base member 2 has a central opening 3.
As shown in FIG. 6, a lead connector 4 is bonded to the upper (or front) surface of the base member 2 to close the opening 3. The lead connector 4 has an upwardly projecting lead coupler 4a, and to its bottom is connected a disk-like electrode 5 made of Ag-AgCl. As shown in FIG. 8, a lead side lead coupler 7 is coupled to the projecting lead coupler 4a. A lead 6 has its one end connected to the lead coupler 7, and its other end is connected to an electrocardiograph (not shown).
To use the electrocardiographic electrode 1 having the above structure for obtaining an electrocardiogram, the base member 2 is bonded to the skin M of the living body, as shown in FIG. 8, and then a recessed portion 7a of the lead side lead coupler 7 is fitted on the projecting lead connector 4a of the lead connector 4 on the side of the electrocardiographic 1, thus coupling the lead side lead coupler 7 to the electrocardiographic electrode 1. In this state, a weak voltage derive from the electrode 5 is coupled through the lead 6 to the electrocardiograph (not shown) for recording.
In an alternative way, the recessed portion 7a of the lead side lead coupler 7 is preliminarily fitted on the projecting lead coupler 4a of the lead connector 4 of the electrocardiographic electrode 1, and then the electrocardiographic electrode 1 with the lead side lead coupler 7 coupled thereto is bonded to the skin M of the living body.
In either one of the ways of use as described above, an electrocardiogram may be obtained. In this use, however the electrocardiographic electrode is used as a consumable, that is, it is discarded when it is removed from the skin after the measurement. Nevertheless, the electrode 5 of the electrocardiographic electrode 1 uses an expensive metal such as Ag-AgCl. Besides, the electrode 5 which leads out a weal voltage directly from the living body, is a separate component from the lead side lead coupler 7 and lead 6 (i.e., lead section) for leading the voltage derived by the electrode 5 to the electrocardiograph. Therefore, complicated assembling is necessary, leading to high cost of manufacture. Particularly, since a plurality of electrocardiographic electrodes is used in combination, the cost problem is substantial. Therefore, development of an electrocardiographic electrode which can be manufactured less expensively has been expected.
In a further aspect, as is seen from FIG. 9, for obtaining an electrocardiogram it is necessary to apply electrocardiographic electrode 1 to the skin M of the living body not only at a single position but at two or more, and recently more than one hundred, positions. With the prior art electrocardiographic electrode 1, in which the electrode 5 and lead 6 are separate components, each lead 6 is coupled to each electrode 1. Since there is a large number of positions, at which an electrode 1 has to be applied to the skin M, therefore, the application of electrodes requires a long time and is very cumbersome. Further, since a large number of leads 6 are wired to the skin M of the living body, there is a possibility that the lead 6 is pulled unconsciously, resulting in detachment of the electrode 1 from the skin M during the electrocardiographic measurement.
Further, for some seriously ill patients electrocardiographic electrodes 1 have to be applied to the back as well. When the patient is lying, he or she will be uncomfortable due to the electrocardiographic electrodes held on the back. Further, prior art electrocardiographic electrodes fail to fit the living body satisfactorily.
Moreover, when the electrode 5 is held in direct close contact with the skin, there is a problem that contact resistance at the skin surface makes the measurement of weak voltage erroneous. To cope with this problem, a water-containing gel member 8, as shown in FIG. 10, is fitted in the opening 3 of the electrocardiographic electrode 1 for reducing the contact resistance of the living body before the electrode is applied to the skin M of the living body as shown in FIG. 8. Where a number of electrocardiographic electrodes 1 are applied at a time, however, the fitting of water-containing gel members 8 in each electrocardiographic electrode 5 is cumbersome and time consuming.